German Patent Application No. 40 00 903 shows a micromechanical sensor configured as an acceleration sensor which is manufactured on the basis of silicon micromechanics. The sensor includes a support made of a silicon substrate with an epitaxial layer of silicon applied to the silicon substrate. A part of the epitaxial layer is laid bare by an etching process to provide micromechanical deflection parts in the form of tongues. One or more tongues are suspended for this purpose from one or more webs and are deflected from the rest of the sensor structure under the action of a force on the sensor. Means are furthermore provided for evaluating the deflection.
German Patent Application No. 40 03 473 discusses taking crystallographic angles of a single-crystal silicon wafer into consideration in connection with the development and arrangement, as well as for the etching process. To provide a means for evaluating the deflection of the tongues, individual electrodes, which are each electrically insulated from each other, are provided so that a capacitative change between tongue and electrode is measurable.
The laying bare of the tongues as a component of the epitaxial layer is effected by means of a rear etching. This constitutes an additional process step as compared with an ordinary bipolar process.
From PCT Application No. WO 92/03740, it is known to apply, on a support made of a silicon substrate, a layer of polycrystalline silicon onto a silicon-oxide layer having contact windows in an LPCVD process (low pressure chemical vapor disposed). The silicon oxide layer is removed by an etching process, as a result of which the polycrystalline silicon layer is present at a distance from the silicon substrate as tongue or electrode on the supports formed in the contact windows. The deposition rate of low voltage LPCVD-poly is about 60 .ANG./min and is thus very slight as compared with the separation rate of about 1 .mu./min of epitactic polysilicon. Due to this, for reasons of process economy, only relatively thin LPCVD layers can be produced. As the result, the working capacity of a lateral acceleration sensor, for example, is limited by the correspondingly small layer thicknesses of the tongues. Furthermore, additional silicon depositions are necessary for this procedure, as compared with a conventional bipolar process.